kernel/sched/swait.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 #include <linux/sched/signal.h>
   3 #include <linux/swait.h>
   4
   5 void __init_swait_queue_head(struct swait_queue_head *q, const char *name,
   6                              struct lock_class_key *key)
   7 {
   8         raw_spin_lock_init(&q->lock);
   9         lockdep_set_class_and_name(&q->lock, key, name);
  10         INIT_LIST_HEAD(&q->task_list);
  11 }
  12 EXPORT_SYMBOL(__init_swait_queue_head);
  13
  14 /*
  15  * The thing about the wake_up_state() return value; I think we can ignore it.
  16  *
  17  * If for some reason it would return 0, that means the previously waiting
  18  * task is already running, so it will observe condition true (or has already).
  19  */
  20 void swake_up_locked(struct swait_queue_head *q)
  21 {
  22         struct swait_queue *curr;
  23
  24         if (list_empty(&q->task_list))
  25                 return;
  26
  27         curr = list_first_entry(&q->task_list, typeof(*curr), task_list);
  28         wake_up_process(curr->task);
  29         list_del_init(&curr->task_list);
  30 }
  31 EXPORT_SYMBOL(swake_up_locked);
  32
  33 void swake_up(struct swait_queue_head *q)
  34 {
  35         unsigned long flags;
  36
  37         raw_spin_lock_irqsave(&q->lock, flags);
  38         swake_up_locked(q);
  39         raw_spin_unlock_irqrestore(&q->lock, flags);
  40 }
  41 EXPORT_SYMBOL(swake_up);
  42
  43 /*
  44  * Does not allow usage from IRQ disabled, since we must be able to
  45  * release IRQs to guarantee bounded hold time.
  46  */
  47 void swake_up_all(struct swait_queue_head *q)
  48 {
  49         struct swait_queue *curr;
  50         LIST_HEAD(tmp);
  51
  52         raw_spin_lock_irq(&q->lock);
  53         list_splice_init(&q->task_list, &tmp);
  54         while (!list_empty(&tmp)) {
  55                 curr = list_first_entry(&tmp, typeof(*curr), task_list);
  56
  57                 wake_up_state(curr->task, TASK_NORMAL);
  58                 list_del_init(&curr->task_list);
  59
  60                 if (list_empty(&tmp))
  61                         break;
  62
  63                 raw_spin_unlock_irq(&q->lock);
  64                 raw_spin_lock_irq(&q->lock);
  65         }
  66         raw_spin_unlock_irq(&q->lock);
  67 }
  68 EXPORT_SYMBOL(swake_up_all);
  69
  70 void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait)
  71 {
  72         wait->task = current;
  73         if (list_empty(&wait->task_list))
  74                 list_add(&wait->task_list, &q->task_list);
  75 }
  76
  77 void prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait, int state)
  78 {
  79         unsigned long flags;
  80
  81         raw_spin_lock_irqsave(&q->lock, flags);
  82         __prepare_to_swait(q, wait);
  83         set_current_state(state);
  84         raw_spin_unlock_irqrestore(&q->lock, flags);
  85 }
  86 EXPORT_SYMBOL(prepare_to_swait);
  87
  88 long prepare_to_swait_event(struct swait_queue_head *q, struct swait_queue *wait, int state)
  89 {
  90         if (signal_pending_state(state, current))
  91                 return -ERESTARTSYS;
  92
  93         prepare_to_swait(q, wait, state);
  94
  95         return 0;
  96 }
  97 EXPORT_SYMBOL(prepare_to_swait_event);
  98
  99 void __finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 100 {
 101         __set_current_state(TASK_RUNNING);
 102         if (!list_empty(&wait->task_list))
 103                 list_del_init(&wait->task_list);
 104 }
 105
 106 void finish_swait(struct swait_queue_head *q, struct swait_queue *wait)
 107 {
 108         unsigned long flags;
 109
 110         __set_current_state(TASK_RUNNING);
 111
 112         if (!list_empty_careful(&wait->task_list)) {
 113                 raw_spin_lock_irqsave(&q->lock, flags);
 114                 list_del_init(&wait->task_list);
 115                 raw_spin_unlock_irqrestore(&q->lock, flags);
 116         }
 117 }
 118 EXPORT_SYMBOL(finish_swait);